Field of the Invention
The present invention relates to a device comprising an electrical cable and/or an electrical cable fitting, and a space charge trapping layer.
The present invention is typically but not exclusively applicable to the fields of power cables and their fittings, for the transmission of DC current.
Description of the Related Art
Power cables are typically medium-voltage (especially from 6 to 45-60 kV) or high-voltage (especially higher than 60 kV, and possibly ranging up to 800 kV) cables, especially for DC current (i.e. DC voltage) transmission.
Medium- or high-voltage power cables typically comprise an elongate central electrical conductor and, in succession and coaxially about this electrical conductor, a first semiconductor layer (or internal layer), an electrically insulating layer, and a second semiconductor layer (or external layer). These layers are based on one or more polymers and may or may not be cross-linked.
Examples of power cable fittings include power cable joints and terminations, these fittings conventionally comprising one or more semiconductor elements.
The discontinuity in the electrical properties between the semiconductor elements of said fittings, and the electrically insulating layer of this type of cable may lead to a local strengthening of the electric field due to accumulation of space charge or space charges under the action of an electric field.
This electric field localized at the interface between the fitting and the cable may thus lead the electrical cable and/or fitting in question to breakdown, and is therefore a considerable threat to the reliability of a power transmission network with the well-known economic consequences engendered by power outages.